The invention relates to a hydraulic grapple for attachment to a movable arm.
Hydraulic grapples have two jaws that can move relative to each other to clamp onto objects. Similar to many other construction industry tools, such as buckets and the like, grapples can couple to a dipper stick at the end of an articulated arm of a heavy construction equipment. Grapples typically include structure that couples to the end of the arm's dipper stick at a dipper pivot, and structure that couples to a linkage to the arm's bucket cylinder at a link pivot.
U.S. Pat. No. 4,248,471 describes a grapple that includes a front jaw strut that is articulated from the dipper pivot and is coupled to the link pivot. The rear jaw is articulated from a part of the front jaw that extends past the dipper pivot. A strut extends from the back side of the rear jaw and connects to the underside of the dipperstick. Extending the rod of the bucket cylinder on the arm closes the front jaw against the rear jaw, and retracting the bucket cylinder rod opens the grapple.
Strut-type grapples can also couple indirectly to the equipment arm with the use of a tool coupler. For example, the QC Grapple, provided by Wain-Roy, Inc. of Hubbardston, Mass., is designed to work with the Wain-Roy TOOLHITCHO.RTM. Coupler System, which is described in U.S. Pat. No. 4,311,428.
Other grapples lack the strut to the rear jaw. For example, U.S. Pat. No. 4,542,929 describes a clam-type grapple having two movable jaws, each articulated from a coupling portion and each actuated by a hydraulic cylinder. The coupling portion connects to both the dipper pivot and to the link pivot.
Some strutless grapples include a rotation mechanism. For example, the clam-type grapple described in U.S. Pat. No. 4,542,929 includes a mechanism that rotates the grapple about an axis that bisects the angle between the jaws. The rotation axis is approximately perpendicular to an imaginary line that extends through the dipper pivot and the link pivot.
U.S. Pat. No. 4,017,114 also describes a grapple having a mechanism for rotating the grapple about a similarly oriented axis. This grapple differs from the clam-type grapple in that it has a fixed jaw attached to the rotation mechanism. A proximal end of a movable jaw is articulated from a proximal end of the fixed jaw closest to the coupling to the arm of the equipment. The fixed jaw is substantially aligned with the rotation axis. A single grapple cylinder actuates the movable jaw. In both types of grapples with rotation mechanisms, extending and retracting the bucket cylinder rotates the entire grapple around the dipper pivot.